1. Field of the Invention
This invention relates to a welding beveling (groove) of a T-joint for a member to be welded to a rib which varies in thickness, along its length for example as in a joint of an impeller assembly in a compressor.
2. Description of the Prior Art
The welding beveling of a T-joint as shown in FIGS. 1 and 7 is known in order to perform a welded assembly of an impeller in a compressor. However, when the thickness of a rib 2 of a lower plate 1 changes in the direction of the length of the rib as shown (right angular direction against the paper) in FIG. 1, particularly where the thickness of the rib varies from a super thin thickness of about 2 mm to a thickness of 8 to 10 mm, the formation of the weld penetration in the rib 2, the penetration at beveling 4 of an upper plate 3, and a fixed uniformity of the penetration bead are difficult to obtain by merely changing the welding conditions with respect to the welding beveling where the overlapping of the upper plate 3 with the rib 2 is adapted to be a fixed dimension corresponding to the change of the thickness of the rib 2.
As described above, when the thickness of the rib 2 changes from the super thin thickness of about 2 mm to 8-10 mm the change of the welding condition at the welding beveling having a fixed overlap cannot produce a stable and uniform penetration bead at the super-thin thickness portion even if a small current is used as a welding condition because the heat is accumulated at the side of the rib 2 and causes; deep penetration due to small heat transfer at the side of the rib 2.
Further, in a T-joint, it is necessary to set the upper plate 3 on the upper surface of the rib 2 in order to determine the clearance (the height of the rib). In the prior art, when the upper plate 3 at beveling 4 is set on the whole surface of the rib 2, the positions of the right and left sides, and of the front and the rear of the beveling 4 and the rib 2 cannot be observed. Further, when the set position is out of place, a uniform bead cannot be obtained due to forming a large penetration bead, or discontinuance thereof.